High - Speed Path Length Scanning for Optical Coherence Tomography

Current optical coherence tomography (OCT) imaging technology allows acquisition of micronscale images of tissue microstructure at rates of several frames per second over cross-sectional areas of a few square millimeters. These rates and ranges are limited by the mechanical scanning mechanism of the galvonometers currently employed in optical delay lines. New developments in OCT technology require a simple, high-speed scanning delay line capable of supporting broad spectral bandwidths. A portable, broadband, high-speed scanning technique would remove motion artifacts and allow ultrahigh resolution, spectroscopically-resolved OCT imaging to be performed in vivo, enabling OCT to be evaluated for detecting early neoplastic changes and cancers in a clinical setting. This project develops and evaluates a novel high-speed delay line capable of scanning over several millimeters at a 1 kHz repetition frequency. The delay line uses a multi-pass mirror geometry based on a Herriott-type cell which accumulates differential delays in each pass. The delay line is electromagnetically-actuated using a commercially available audio speaker. The system enables image acquisition at a rate of 4 frames per second, allowing motion-artifact free in vivo images to be obtained. The delay line was incorporated into the reference arm of an existing OCT system and evaluated during imaging of an anesthesized Xenopus laevis (African frog) tadpole, a common developmental biology model. Path length scanning over 3.1 mm at a 1 kHz repetition frequency is demonstrated. Higher scan repetition frequencies are feasible and are currently being investigated. Thesis supervisor: Professor James G. Fujimoto Department of Electrical Engineering and Computer Science